The Brookdale Psychiatric Hospital is a crumbling institution which barely has enough money to remain open. Formerly a prison, it sits on top of a warren of tunnels and sewage system viaducts. But Brookdale has a secret, only known by one person. There is something living in the tunnels and it has developed a taste for human blood.

You might be thinking of the 1984 movie of the same name (or sometimes known as, Rats - Night Of Terror), which has a bit of a cult following. This one was made in 2003 and is just another in a long line of cheap horror movies with really cheap computer generated 'monsters', like Octopus, Spiders, Crocodile etc....except this one has Rats.